In this work, new graphene-based screen-printed electrodes are proposed as a new, cheaper alternative to more common electrodes for determination of dopamine. Electrodes were designed, manufactured and tested to look for correlations between different graphene weight percentages used in electrodes and oxidation peaks and sensitivity in dopamine determination. All electrodes were tested using cyclic voltammetry. For a reference, graphite electrodes were tested. With sensitivity of 0.0161 μA/μM and detection limit of 5.549 μM those electrodes showed potential promise in use of graphene for electrode material. In electrodes manufacturing, Laroflex and PMMA based vehicles were mixed in with graphene platelets with diameters ranging over 2 μm and thickness between 8-15 nm. Initial tests with electrodes screen printed with graphene layers of 150 μM showed very low response. 0.0077 μA/μM sensitivity and 11.970 μM detection limit were achieved with Laroflex based electrodes. Further testing with thicker layers gave more impressive results with detection limit going as low as 1.349 μM and 0.1343 μA/μM sensitivity. Such results bring those electrodes to comparable level with other electrodes available.
The paper includes description of a novel approach for producing stretchable, conductive interconnects for wearable electronics. At first the current state-of-the-art and market solutions were reviewed, and then we described our optimization of the composition of conductive pastes used in the screen printing technology. Namely, the ratios of TPU (Thermoplastic Polyurethane) dissolved in DMF (Dimethylformamide) as a carrier were empirically optimized, followed by adding silver flakes as a filler. To test the quality of the final paste, a number of tracks were printed on 100% cotton fabric substrate. Changes in the electrical resistance were measured while the samples were stretched, twisted, soaked, and washed. Despite being pushed to the limits of the substrate physical capabilities, printed interconnects still retained their conductive properties, with electrical resistance increasing by no more than 10x relative to initial, very low resistances of a few ohms, and then decreasing over time. We have also discovered that ironing the samples did not destroy the tracks. Instead, the ironing process regenerated them, and their electrical resistances returned to initial values or even decreased. The method described in this paper is innovative because it enables printing directly onto textiles and the usage of a non-synthetic textile substrate while still retaining robustness in electrical conductivity.
In the world of constant facilities of human life, as well as improving the comfort of patients, there are more and more reports on non-invasive methods of testing and health related procedures. One of the most common invasive procedures performed by patients is the procedure of taking blood from the fingertip to the glucose test. It is not surprising, therefore, that the attention of researchers around the world is focused on eliminating the need for invasiveness of these tests. The tendency to facilitate and minimize interference in body coherence concerns all tests with which diabetic patients come in contact. In the light of this trend, a promising idea seems to be the possibility of non-invasive measurements of one of the conditions associated with diabetes - ketoacidosis. Such novel and non-invasive procedure is for example monitoring the amount of acetone exhaled with air by a diabetics suffering from ketoacidosis. In this work we present the sensors of acetone vapors based on titanium oxide and graphene nano-flakes or carbon nanotubes fabricated using a screen printing technology on the ceramic substrate. We have also performed test of sensitivity of fabricated sensors into the acetone gases presence in both room temperature and 150° degrees.